A bluish-green "Phosphorlicht" of living leaves was first observed by Carl von Szutz, an apothecary of Hungary, on the leaves of a garden plant, Phytolacca decanda (Linn), between 9 and 10 p.m. one evening in September, 1800. Szutz picked the leaves and the light continued to shine, sometimes yellowish-green, sometimes bluish, sometimes stronger, sometimes weaker, depending on whether the "Zug der Lade" was stronger or weaker. The phosphorescence lasted until after midnight and then disappeared. The light may have been an electrical phenomenon, although luminous fungi growing on living leaves is a second possibility (As quoted by E. Newton Harvey, in A History of Luminescence, The American Philosophical Society, Philadelphia, pp486, 1957).
Phytoluminescence was first described by Strehler and Arnold in 1951 (Strehler B. L. and Arnold W. 1951, Light production by green plants--J Gen Physiol 34:809-820). This extremely short lived light emission by living green plants is not visible to the unaided eye and not at all related to the observations of von Szutz. This emission of light is part of a photosynthetic reaction by excited states of chlorophyll and is dependent upon photosynthetic electron transport. A reversible injury causes an increase in light output probably by a decrease in photosynthesis diversion of energy to phytoluminescence. Irreversible injury damages the entire photosynthetic mechanism abolishes phytoluminescence. Phytoluminography is two dimensional imaging of phytoluminescence using high sensitivity light amplifiers. The technique was first described by Sundbom and Bjorn in 1977. Its use in early detection of plant stress has been frequently described in Soviet literature. A few selected references are listed:
1) E. Sundbom & L. O. Bjorn, Physiol Plant 40:39-41, 1977 PA1 2) L. O. Bjorn & A. S. Forsberg, IBID 47:215-222, 1979 PA1 3) A. A. Krasnovskii, Jr., Yu. V. Kovalev, et al., Biofizika 25(5), 1980 PA1 4) J. L. Ellenson & R. G. Amundson, Science 215:1104-1106, 1982 PA1 5) R. Blaich, O. Bachmann, & I. Baumberger, Z Naturforsch Sect C Biosci 37 (5-6):452-457, 1982 PA1 P. F. Daley, K. Raschke, J. T. Ball, & J. A. Berry, Plant Physiol 90: 1233-1238, 1989
Phytoluminescence has been arbitrarily divided into chlorophyll fluorescence and delayed light emission by all the authors. We attribute this division to insensitive imaging techniques and can demonstrate these to be parts of a negative exponential luminescence decay. The prior art involves large, expensive apparatuses using conventional air coupled lenses, mechanical shutters, long optical paths and light sources that do not resemble sunlight. Since the apparatuses are not hand-held or battery operated, they are inconvenient for use outside the laboratory. This limits the use of this valuable technique and puts it beyond the reach of common farmers and horticulturists.
Schematics of typical apparatuses using the prior art are reproduced in FIGS. 1, 2, and 3 as published in references 1, and respectively.